Crankcase induction valve for two-cycle engines



Oct. 7, 1952 E. c. Kll-:KHAEFER 2,612,882

CRANKCASE NDUCTION VALVE FOR TWO-CYCLE'. ENGINES 2 SHEETS--SHEET 1 Filed Sept. 23, 1949 Oc t. 7, 1952 Y E; c; KlEKHAEFl-:R 2,612,882

CRANKCASE INDUCTION VALVE FOR TWO-CYCLE ENGINES Filed sept. 25, 1949 A 2 SHEETS-SHEET 2` (0560 CZOSED off/v IN V EN TOR.

Patented Oct. 7, 1952 CRANKCASE VINDUCTION VALVE FOB TWO-CYCLE ENGINES Elmer ,Gr."Kiekhaejfer, Cedarburg, Wis. Application September Z3,'1&49,SerialNo,'1l7;325

y .i 6; Claims.

"This `invention relates to two-cycle,` internal- `combustion engines and particularly tothe crankcase induction system -and valve lmeans control- "ling the lsame for alternate firing, adjacent cylv'- inders of such engines.

"The" invention provides a valve unit to be asfsembled on the'crankshaft providing an induction passage extending between and opening into separate crank'chambers and having oppositely "disposed -pairs of reed valves controlling the induction of the respective crank chambers. The reed valvesarearranged about the crankshaft of j therengine and provide for the introduction of a larger fuel charge under'conditions which assure vvgreaterfuel efficiency and engine power output fr; at high speed.

A'prncipal object ofthe invention is to adapt v:fcranlrcase reed valves to high-engine speeds for nigreater engine output at such speeds under load.

Another object of the invention is to provide for'themore complete ,induction of the fuel mix- ;ture intoadjacent alternately fired cylinders at nhigh-speeds.

, A further object is to provide apassage for the iiow ofl fuel` mixture into the adjacent crank chambers lwith a minimum of obstructions and changes of Vdirection of now.

AAnother object-is to time theinduction ofthe fuel mixture into the adjacent cylinders so that f the flow is substantially continuous and proceeds without surging or pulsating particularly at high igspeeds.

A more particular object `isto extend the period ofinduction of eachcrank chamber to vthe :com-

mencement of theinduction-cycle of the adjacent chamber.

Another object is toenlarge the induction cycle lof each chamber for maximum scavenging and -recharging of the cylinder, affording higheren- Y gine speeds and'greater engine'efciency.

A further object is to ensure the immediate f and full opening of the valves at high speeds Nvithout lag and incompleteinduction.

Another-'object is to ensure the immediate and complete closing of the reeds at the end ofthe induction cycletoprevent back pressure and loss `of engine eciency and eliminate any possibility of re reaching the carburetor-incase of back- ,.ringroi the fuelcharge in the crank chamber.

, -Another objectofthe ,invention isato provide for valve operation gat higher` speeds without loss offvalveefiiciency, at; the lower engine speeds.

lAnother object is to introduce the fuel mixture into the crank chamber sofas to veffect a further Gr.more .complete atomization; yof, the. liquid. fuel 'within the crank chamber.

(Cl. 12S-,73)

yAnother object is toI direct; at least a :partici Y the fuel mixture entering thecrankwchamber' 1 2--2 of Fig. v1;

into the cylinder below the pistonwtofcoolffthe i Same.

' These. and other `.objects and'. advantages-,will be set forth inthe followingdescription-nf a preferred embodiment of theinvention as illus- .trated in'the accompanying drawings.

v show the valve unit;

AFig 2 is a horizontalsection through-thefsupper cylinder -of the engine shown in-"@F-ig; y 11 onrline Fig. 3 is a horizontal .section..'fhrpughxtheinduction passage of-the; enginelshownn-in- Fig. A1 -;,on

t line 3-5-3 Of Fig. l.;

Fig. 4, is. a perspectiveviewof the'unassembled yyvalve V,body members;

yfthroughY ithe--valve portspf goneygofgithef vgalve ductioncycle jofl the engine at low engine ,sp ds',

- Fig-.i 9 is a; Vdiagrammatic Villustrationsofgtheinduction icycle, atfintermediate enginespeeds and '.:indutonfcycle-attained athighrenene speeds:

The crankcaselmernber iigsecuredqtogthecyl- -inder block l, and the .end closure members 8 comprise `the crankcase 9 which; venclo*ses-.cra,nkshaft 2. Thepend bearings `itl supporting nkshaft 2. are lcarried by members @and thepearing and valve unit, l,|, as will bedesrcribedupports crankshaft 2 intermediatenupperandlower crank throws I2 and 13. Unfitrl I'y dividescrankcase 9 into the-respective, separate crankjcham- "The upper andlower cylinder boreslrlfiand Il of block 'l open forwardly intochambersrmfand l ti,v respectively, ,andfcarry the Vpistonsrl 8;.and I9, leljnd '3 ',The intake ports l2l in .ene side;,ofijfeach-cylinder open into a transfer passage 23 i-ing alongsiderthecylinders-imm. :fthe ,corres Jriding The exhaust ports 22 of each cylinder are disposed approximately opposite of ports 2 I and open outwardly into exhaust discharge means, not shown.

Intake ports 2I and exhaust ports 22 of each cylinder I3 and I'I are disposed to be covered and uncovered by the respective piston in the operation of the engine, as will -be described.

The bearing and valve unit II dividing crankcase 9 into the upper and lower chambers I4 and I5 includes the two complementary semi-cylindr-ical members 24 having a center bore 25 fitting the center section of crankshaft 2 between crank throws I2 and I3 journally supporting the crankshaft.

The outer diameter of members 24 fits accurately the inner dimensions of crankcase 8 to divide the same into the separate airtight chambers, as described. Members 24 are assembled on crankshaft 2 and joined by the screws 26 and assembled in crankcase 9 with the assembly of the crankshaft.

The screw 21 passing through crankcase member 6 secures valve members 24 within crankcase 9 against rotation with crankshaft 2.

The passages 28 in members 23 join forwardly and together register with the opening 29 in crankcase member 6. The passages extend rearwardly on either side of crankshaft 2 and are closed by the section 30 of block I intermediate cylinders I6 and I'I, as shown in Fig. 3.

The valve ports 3I and 32 in the upper and lower planiform end faces of members 24 opening from passages 28 ofthe members into chambers I4 and I5, respectively. are controlled by the flexible reeds 33 and 34 which are normally seated ilat on the upper and lower faces of the members and over the ports. Each of reeds 33 and 34 comprises s. flexible, thin metal member secured at one end adjacent the respective ports 30 and 3I and which is adapted to flex as the opposite free end is lifted by thegreater gas pressures on the side of the reeds facing the ports to uncover and open the ports.

The rockers 35 comprising curved rigid metal members are disposed to limit the opening of reeds 33 and 34 and are shaped to distribute the flexing evenly throughout the length of the reeds.

The slots 36 in the upper and lower faces of members 24 at the base of reeds 33 and 34 provide for any accumulation of dirt beneath the reeds which would otherwise interfere with closing of 'the reeds.

V and I3 into the interior of chambers I4 and I5,

respectively. The two rear reeds 34 of each member 24 are disposed to open rearwardly and toward each other to direct the fuel mixture into the lower end of cylinders I6 and I1 and against rthe underside of pistons I8 and I9.

Corresponding ports 3| and 32 opening into upper and lower chambers I4 and I5, respectively, are diametrically opposite so that reeds 33 and 34 of one chamber close toward the reeds of the other chamber.

The fixed ends of reeds 33 and 34 are located by the pins 39 which project through section 36 of rockers 35 and are secured by the latter and the screws 31.

In the operation of engine I, pistons I8 and I9 reciprocate in opposite directions. Cylinders I6 II are fired alternately by the spark plugs 40 as the corresponding piston reaches the upper end of its stroke providing two power strokes per' crankshaft revolution.

Ports 2I and 22 are disposed to be uncovered by pistons I8 and I9 as the pistons approach they lower end of the power stroke, providing for the exhaust of the cylinders through ports 22 and forl the recharging of the cylinders by the compressed fuel mixture within the corresponding crank chamber through passages 28 and ports 3|. As pistons I8 and I9 move upwardly from the lower position the pistons cover and close ports 2I and 22 and compress the fuel mixture within the cylinders for ignition and the next power stroke.

The carburetor 4I connected to fuel supply means, not shown, is provided with the carbureting passage 42 which is open at one end to receive air for combustion and registers at the other end with opening 29 to deliver the fuel mixture through passages 28 and ports 3I and 32 to chambers I4 and I5, respectively, as will be described.

Pistons 3l and 32, moving upwardly after closing ports 3 I, effect a reduction air pressure within the respective crank chambers and the induction of fuel mixture into the chambers through ports 3| and 32 which are opened by reeds 33 and 34 in response to the greater pressure on the outward sides of the reeds.

After the outward induction stroke of the pistons and concurrently with each downward power stroke reeds 33 and 34 close the corresponding ports 3| or 32 and the pistons effect a compression of the fuel mixture within the respective crank chambers. y

As ports 2I are uncovered by the pistons at the end of the downward power stroke, the fuel mixture is admitted to the respective cylinders through transfer passages 28 from the corresponding crank chambers for recharging of the cylinders as described.

In an engine employing mechanical valves, the low speed induction cycle and that of any higher speeds is xed and remains the same as that of the induction stroke of the engine, as shown in Fig. 9.

At high speeds, under load requiring a fully open throttle, a full fuel charge is not allowed sufricient time to pass into the crank chambers and the chamber is not lled by atmospheric pressure by the time the piston has reached top dead center and the mechanical valves are closed.

In engines heretofore employing reed valves, the induction cycle at various speeds can be extended according to the engine speed but without advantage. At high speeds the chamber continues to be unfilled as the piston travels downwardly in the power stroke and may not be filled until the piston has traveled half the distance of its full downward stroke.

In such cases where the induction cycle continues into the power downstroke of the piston the amount of fuel mixture actually inducted is reduced by the extent to which the crankcase Volume has been reduced by the movement of the piston traveling downwardly. In such cases, furthermore, where the induction cycle continues into the compression cycle, the compression cycle is reduced by a corresponding amount and the fuel transfer and scavenging is reduced correspondingly,

- filntake: passage 11 4 I ofrcarburetor ideands-,ipasagesuaz -saremsub'stantially'i im straight 4linen-:providing a'fcollumnar;LlaniinanfiowA of thegfuela mixiturE'tthrough the:.passagesizdirectly:torgand serving chambers |4 and l5 through ports z3'|::.and:32, .respectivelyjthe .column of fuel mixture, moving at high speed through passages 4| and 28.

attains a moment of inertia according to its mass I@and velocitywhich is directed v.against reeds 33 s.; continues i to.,A move `into the.. chamber i after. the

onfandrthe piston ismovi-ng'gdownwardlyf.jThe

.Y fuelz mixtureV column in passages 4| .andfi28;thus

continues the induction.cyclebeyond the induction stroke'of the piston.

fAccording to the invention, the induction sysvfx-.tern provides -fon continuation of ther-induction zcycle :until the beginning ofthe induction-stroke of the piston of the adjacent crank chamber. For this purpose, the size of ports 3| and 32 and the flexibility and other characteristics of reeds 33 and 34 must be established within limits for an engine of given displacement and crankshaft rotation at high speed.

The reeds should be sufficiently stiff so that they will close positively and quickly when the pressure within the crank chambers on one side of the reeds reaches the pressure directed against the opposite side of the reeds by the column of fuel mixture. The reeds, however, need not be as stiff as would be required in other induction systems by reason of the fact that the closing of the reeds occurs nearer the end of the induction stroke and when the linear velocity of the piston is less and more time for the closing is allowed. The reeds may, therefore, be more readily adapted to low speed operation.

The size of ports 3| and 32 determines the size of reeds 33 and 34 and should be sufficient to allow enough fuel mixture into the carburetor so that the induction cycle is not unnecessarily extended into the compression cycle and so that maximum induction is obtained at high speeds.

The dimensional limitations of the crankcase required for maximum or volumetric efficiency of compression and the size of the reeds required for proper operation and securing within the crankcase are overcome according to the invention by disposing the induction passages 28 adjacent the crankshaft substantially normal thereto in the body of the center main bearing unit substantially as described and allowing for opening clearances of the reeds between the bearing unit and adjacent cheeks of crank throws |2 and I3.

The number of ports 3| and 32 employed for each chamber I4 may vary according to their size and the requirements of the engines.

Various embodiments of the invention may be employed within the scope of the following claims:

I claim:

1. In a two-cycle internal-combustion engine having a pair of alternately flring cylinders, a crankshaft, and a crankcase therefor receiving the fuel mixture for precompression prior to 'transfer to the engine cylinders, a valve unit controlling the induction of fuel mixture into said crankcase comprising a valve body assembled on said crankshaft and disposed to divide said crankcase intoindividual crank chambers, said crankshaft has passed .top dead center, :of: .rota--` ab'odyrrleflning.: arlsubstantiallycolumnar message daptedstoz-receive,ifuelimixturezatmigh .ileiocilesrand-:having-zvaivesportsxarrangedtaboutisaid crankshaftr;.openinggzoppositely :intox respective 5-sprankischamberss.saidepassagefbeingrunobstructed ybetween:the:corresponding:ports of tha-respective.-crankzachamberssfand :flexible reed members carried? bysaid.y valvesbodyenormally `closing said ports andnopening ,the latterrinfresponse; to cyclic pressurei variations:y inntheyV respective :chambers and fthe :pressure of. thegfuel; mixture .by .reason ,slof-its velocity in .said passage. -:betweensaid-.ports .f 2. AIn.- a;twofcycle';internal-combustion engine,

"f a. crankcase.edeninguseparate tadiacentrcrank 15.chambersi and an .z intermediate: .cclumnarfzipasrespondinggchambers l of ,saidcrankcase; pistons .g reciprocating;Y 4oppositely ini .said., cylindersuisand providing. for; the induction; of :fuel mixtureifrom said carbureting means through said passages into corresponding crank chambers, and reed valve means controlling said passage normally closing the same and opening the passage to one chamber in response to the movement of the corresponding piston in one direction, said reed valve means being oppositely disposed and unobstructed therebetween whereby opening of said passage by said reed valve means to one of said chambers is eected by the reaction of the fuel mixture within said passage to the closing of said passage to said other chamber.

3. In a two-cycle alternate-firing, two-cylinder internal-combustion engine, a crankshaft, a crankcase for said crankshaft having a fuel inlet port, crankcase bearing members assembled on said crankshaft dividing said crankcase into individual crank chambers and having fuel manifold induction passages registering with said inlet port and having openings oppositely thereof into said crank chambers, said passages being unobstructed between openings, and oppositely disposed valve reeds closing toward each other and opening and closing the respective passages alternately in response to cyclic pressure variations in the respective chambers.

4. In a two-cycle internal-combustion engine including a crankshaft, a crankcase therefor receiving the fuel mixture for precompression, and at least two cylinders opening into said crankcase, a valve unit controlling the induction of fuel mixture into said crankcase comprising a valve body assembled on said crankshaft and disposed to divide said crankcase into individual crank chambers, said body being adapted to receive fuel mixture and having valve ports in opposite ends thereof arranged about said crankshaft and opening into respective crank chambers, and exible reed members carried by said valve body normally closing said ports and opening and closing the same in response to cyclic pressure variations in the respective chambers, at least one of said ports and reed members being disposed to direct the induction fuel mixture of a chamber into the corresponding cylinder.

5. In an engine including at least two alternate ring cylinders, a crankshaft for said engine and a crankcase providing a separate fuel induction compression chamber including the lower portion of the corresponding cylinder for each crank of said shaft. fuel induction passages provided by said crankcase intermediate said chambers and on either side of said crankshaft, and oppositely disposed valved ports arranged about said crankshaft opening from said passages into said respective chambers in the direction of the corresponding cylinders and in response to cyclic pressure variations therein.

6. In a two-cycle, alternate-ming, twol-cylinder engine having a crankcase, crankcase bearing members dening separate crankcase chambers, a crankcase induction system therefor comprising carbureting means disposed adjacent said chambers, a passage within each of said bearing members communicating with said carbureting means at one end and closed by said crankcase at the opposite end and having intermediate ports opening into said chambers and adapted to define an air column between said chambers, and reed valves disposed over said ports normally closing the latter and 20 including oppositely disposed reeds closing toward each other to control said ports, each of chamber.

ELMER C. IUEKHAEFER.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,845,702 Evinrude Feb. 16, 1932 2,103,564 Tanner Dec. 28, 1937 2,374,959 Ruppe May 1, 1945 2,459,594 Smith Jan. 18, 1949 FOREIGN PATENTS Number Country Date 204,948 Great Britain Oct. 11, 1923 252,836 Great Britain June 6, 1926 

